Brake shoe



July 11, 1933.

G. J THOMAS BRAKE snon Filed March 25, 1929 2 Sheets-Sheet 1 IN V EN TOR.

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G. J. THOMAS July 11,1933.

BRAKE SHOE 2 Sheets-Sheet 2 Filed larch 25, 1929 INVENTOR. @1321 QM BY QGa z:

ATTORN Patented Juli u UNITED ST E-s PATENT OFFICE GEORGE :oszsrn moms, or Darren, mm, nssronoa 'ro nmmrx 1mm coirrm. Q1 BOU'IHBBHD, A OOR POBATION OF ILLINOIS BRAKE SHOE Application fled Iii-ch25, 1929. Serial No. 849,746.

This invention relates to brakes, and is illustrated as embodied in an internal expandmg automobile brake. An object of the invention is to.arrange the brake shoes," or

. their equivalents, so that the friction surfaces (e. g. of the brake lining) will have a maximum degree of effective engagement with the brake drum.

Having this object in view I bring the friction surfaces on adjacent shoes, or other friction devices, immediately adjacent each other at the heels of the shoes, the necessary throw or extent of angular movement of the heels of the shoes-i. e. of the ends of the friction surfaces nearest the anchors,-

being obtained by positioning each of the anchors well past the end of the other shoe, thus overlapping or cross-anchoring the shoes. When possible, the anchor should be '20 set back between the-ends of the friction surface of the other shoe.

In the embodiment illustrated in the drawings, the anchored ends of the shoes overlap as described above, while the free ends, ar-

26 ranged adjacent each other across the drum from the anchors, are engaged by an applyin device such as a double cam.

other feature of novelty relates to securing intimate contact of a friction mem- 80 bar with the drum, while at the same time retaining control over. it to obviate points of infinite pressure with the resultant grabbing characteristics. This I propose to accomplish by making the shoe relatively flexible adjacent its free and applying end where the wrapping or self energizing effect is the greatest, and further making the anchored end substantially rigid so that applied ressure here is distributed to obviate grab ing. The individual characteristics of a rigid and 'a flexible shoe are thus combined in a single integral friction device permitting the powerful servo efiectand at the same time retainin control of the shoe to obviate grabbing. 3 further object of my invention relates to the provision of a shoe having an effective lining contact area of more than 180, thus minimizing the wear per unit area. As a particular feature of such a shoe, I adjust its position with respect to the brake drum so that'it is eccentric thereto in released position and by virtue of its semi-flexible nature is capable of being fully applied and subsequently fully released. Such a function is impossible with a rigid shoe contactin with the drum over more than 180 thereo much as such a rigid shoe is incapableof being released.

With my construction I obtain full contact of the relatively'long shoe, the point of initial contact being spaced from the applying end of the shoe a distance which is a function of the lining clearance with the shoe released. Subsequent appl 'n pressure effects an application of the 53x5) shoe, which through its self-energizing action then efl'ects an application of the ri 'd end of the shoe, thus completing the ull lining contact which is the desideratum.

The abovev and other objects and features of the invention, including various novel combinations of parts and desirable particular constructions, will be apparent from the following description of the illustrative embodiment shown in the accompanying drawings, in which:

Figure 1 is a vertical section throu h the brake, just inside the head of the rake drum, and showing the shoes in side elevation 2-2 of Figure 1, showing the anchor arrangement;

Fi ure 3 is a view similar to Figure 1, the lining being removed to give suflicientspace to indicate diagrammatically the action of the shoes; and a Figure 4 is asomewhat modified form of brake comprising a very long semi-flexible inas- 1e end of the a Figure 2 is a partial section on the line 45 double purpose of secllri tilpn forming a friction facefor the S I I An important feature of the invention relates to arranging the anchors-of. the brake so that the shoesoverlap each other thus permitting the adjacent ends of the 18 at the heels 20 and 22 to be brought very close together. To this end, shoe 14 is anchored on a pivot 24 between the ends of the friction face of shoe 16, the web of shoe 16 beingcut awa at 26 to permit of this arrangement, w e anchor 28 for shoes 16 similarly arranged between the ends of shoe 14, which is cutaway at 30. w

The brake is applied, against the resistance of a suitable return spring 32, by means such J as a double cam 34 arranged acrossfthe drum from the anchors 24 and 28. As shown in- Figure 4 a sprin 33 may also be pro- 90 vided to determine, in conjunction with an eficentric stop 29, the idle position of the --s oe.

An important feature of novelty relates to forming the shoes to be relativel flexible '25 adjacent their free ends, where t ey' have their maximum self-energizin or wrapping action bv the wed g force the drum, for

example by reducing the depth of the centralstifienmg flange, while at the same time guarding a ainst grabbingb ta ring web towar the anchor until t e 0e is substantially rigid at its anchored end. This permits absolute control of the shoe by cam 34 and spring 32, while at the same time 35 there is a high degree of wedging or servo action by the rotat' drum on the shoe (on shoe 16-when the rum is turning clockwise, and on shoe 14 when in the oppositedirection in the form shown in Figures 1,

2 and 3.)

- An important object of overlappin the shoes as described above is to bring the eels 20 and 22 as close together as possible,- i. e. to minimize the angle A ,-for the a greater area of engagement with the drum,-and of supporting the entire drum to prevent distorion.

With a twosshoe brake such as selected for illustration the angular length B of the lining on the shoe 16 may be ater than. ,,180; the greater the length 0 lining the more effective it will be, while the less will be the clearance at the point (or 22) when the brake is released, with a given an- A, gular releasing movement of the shoe. Conversely, the smaller the angle B is made,

the less efiective. angular length the lining" will have, and the more clearance will-be secured when the brake is released.

D The a proach of the lining (i. e. of point 20 or 22 to the anchor 24 (or 28) is thus definitely limited to a certain minimum angle C which will give the'necessary clearance when the brake 1s released. In an ordinary thetwo-shoe brake, therefore there is a' gap at least double the angle 0 between the ends of the linin 'on the two sh at their anchored en instead of the :m gap A when the novel cross-anchored shoes are used. The nearer'anchors 24 and 28 are to. the periphery of the drum, the'shorter the angle may be made. .On the other hand t e 368ml tlaxheanchor'zhare'to the cen ter of the rum, t e greater e wedgin' g or servo action of the drum on the shoes. In any given case, the radial positions of the anchors will have to be selected according to the wed g or servo action desired, to 've as lig t a pedal pressure as may be deslred, whereupon the necessity for a certain clearance at 20 (or 22) will fix the size of the an le C.

A further and very important eature of I my invention relates to the virtue of the particular shoe employed in permitting a lining contact of more than 180. As disclosed in Figure 1 and accentuated in Figure 4, both the shoe and its lining are made more than 180 in length, there y increasing the area of lining in drum contact over at of the conventional shoe. Now it becomes necessary by'virtue of such a construction to so construct the shoe as to make it capable of being released from the drum in brake 05 position for with the conventional rigid shoe this is obviously impossible. This 1s made possible by making one end of the shoe-flexible, as previousl described. With application of thecam e long shoe first contactsat or about the point D remote from the applying end of the shoe which assumes the'gmition indicated by the dotted lines in igure 3. Subseq pressure effects a uent cam distortion of the flexible end of the shoe into full drum contact whereupon the wedging or wrapping action of the drum eflects a movement of said end around the drum forcing the rigid end of the shoe into drum contact. The complete application of more than 180 of lining is thus efiected, the shoe being fully controllable.

In the modification disclosed in Figure 4, the short shoe 15 disclosed is preferably made rigid, thus combining in one brake both rigid and semi-rigid shoes with the resultant advantages flowing therefrom, it being understood that the rigid shoe has advantages such ,as strength and ease of adjustment not posfiled March 25,1927, which has now matured into patent No. 1,741,186 and Serial No. 743,-

877 filed October 16, 1924, issued as Patent No. 1,801,397, dated April 21, 1931.

I claim: a

1. A brake shoe comprising a rim member and a web member, means adjacent one end of said web member whereby said shoe may be anchored, means adjacent the other end of ing means, said web member bein of greater radial depth adjacent said anc oring end than adjacent said other end, said shoe extending substantially. 180 in length.

3. A brake shoe comprising a r1m member and a web member, means at one end of said web member whereby said shoe may be anchored, means at the other end of said web member for engagement by applying means, said web member being flexible at said applying end relatively to said anchoring end, said brake shoe extending substantially 180 in lenlgth.

n testimony whereof, I have hereunto signed my name.

GEORGE JOSEPH THOMAS. 

